Conventionally, a reading device to read a code symbol such as a barcode or a two-dimensional code has been known as an optical information reading device to read optical information on a subject to be read by acquiring an image of the subject to be read with an image pickup portion and analyzing the image.
In this reading device, to facilitate aiming by a user, a mark indicating the position of image pickup with the image pickup portion is formed by irradiation on the subject to be read.
For example, as shown in FIG. 18, a reading device 200 forms a mark 201 indicating an image pickup range with the image pickup portion, a mark 202 indicating the width of the image pickup range, and a mark 203 indicating the center of the image pickup range, by light beam irradiation. The various shapes of light beams from the reading device 200 are emitted onto the subject to be read, and marks in the shapes of the beams are formed on the subject to be read. Then the user easily fits a code symbol within the image pickup range of the image pickup portion by aligning the marks with the position of the code symbol to be read, and reads the code symbol with the reading device.
This type of reading device to form the marks is disclosed in e.g. PTL1 to PTL5.
Note that in PTL5, it is described that whether or not a distance from the reading device to the subject to be read is within a range for excellent reading is automatically determined, based on whether or not a pattern drawn with the marker light on the subject to be read is blurred.